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3.1 notes - STAT3000 Chapter 3 Producing Data Data...

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STAT3000 Chapter 3: Producing Data Data Collection 1) Population -- the entire group under study 2) Census -- a count of the entire population 3) Sample – a subset of the population Two types of studies: observational study – observes individuals and measures variables of interest but does not influence the responses experiment - actively impose a treatment to observe (and measure) the response. To see the response to a change, we must impose the change. 92
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Observational studies are performed for two reasons : 1) To learn characteristics of a population; 2) To determine whether there is an association between two or more variables where the values of the variables have already been determined. Note: Observational studies are very useful tools for determining whether there is a relation between two variables, but it requires a designed experiment to isolate the cause and effect of the relation. _______________________________________ response variable – measures an outcome of a study explanatory variable – explains or influences changes in a response variable The response variable depends on the explanatory variable. 93
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Ex : A survey is conducted asking 400 people, “Do you prefer Coke or Pepsi?” Is this an observational study or an experiment? Ex : While shopping, 200 people are asked to perform a taste test in which they drink from two unmarked cups. They are then asked which drink they prefer. Identify the population and the sample: Ex : A business school researcher wants to know what factors affect the survival and success of small businesses. He selects a sample of 150 eating-and- drinking establishments from those listed in the telephone directory yellow pages in a large city. Identify the population, the sample, the statistic or parameter: Ex : A member of Congress wants to know if her constituents support proposed legislation on health care reform. Her staff reports that out of 228 randomly selected people, 193 support reform but oppose the current draft. 94
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This note was uploaded on 06/05/2011 for the course STAT 3000 taught by Professor Staff during the Spring '08 term at UGA.

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3.1 notes - STAT3000 Chapter 3 Producing Data Data...

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